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The necessity of accelerating towards carbon neutrality has been further pushed in recent times. Therefore, with the aim of developing smart grids, new Intelligent Electronic Devices (IEDs) are being widely installed. In this regard, Low Power Current Transformers (LPCTs) are replacing traditional inductive current transformers (CTs). Among these, Rogowski coils feature high linearity, reduced dimensions, and wide bandwidth in comparison to CTs. Hence, this work presents a study on a particular type of LPCT, the Rogowski coil, which is extensively used nowadays. In detail, temperature and humidity are simultaneously applied to three commercial Rogowski coils when measuring off-nominal, hence distorted, currents. The LPCTs performances are evaluated in terms of power quality indexes, Total Harmonic Distortion (THD) and single harmonic evaluation. From the results, THD is not significantly affected by the combined temperature/humidity presence. However, a deep analysis on the single harmonic demonstrated how they are strongly correlated to such influence quantities. It is interesting to highlight that each of the three devices under test present different behaviors. It is then crucial to in deep the investigation on the influence quantities affecting LPCTs. Furthermore, International Standards should include new details and test procedures to assess the effect on the LPCTs accuracy due to such quantities.

In the last few years it has been confirmed that the monitoring is not an exclusive of the transmission network (TN) anymore. In fact, the distribution network (DN) is experiencing a significant deployment of intelligent electronic devices (IEDs) capable of enabling the monitoring and control of both the medium and low voltage sides (MV and LV) of the DN. Such a network revolution is strongly supported by the fact that renewable energy sources are spreading among the DN, introducing problems likes (i) voltage unbalance, (ii) degradation of the power quality, (iii) frequency deviations and inertia reduction, etc. In light of the above, this paper presents the design, development, and characterization of a low-cost network monitoring unit. The device, specifically developed for LV networks, has been designed according to the requirements defined by the utilities. In the paper, the design choices, the device characteristics and the metrological characterization are described. From the results it can be clearly concluded that the device may become an affordable key asset to be deployed in LV networks. In fact, it enables system operators to fully monitor, control, and promptly intervene on their networks.

This work deals with the assessment of an experimental setup for the CO 2 measurement inside the cabin of an electric crane. Different operating and ventilation conditions are compared and the optimal positioning of the CO 2 sensors are discussed. In particular, the results obtained by some sensors placed around the cabin occupant are compared with three sensors positioned in the breathing zone. In all the ventilation modes, a flux of 66 g/h of pure CO 2 is introduced inside the cabin, to simulate the breathing of a driver. We studied three different operating conditions: heating mode, ventilation mode and cooling mode. In each condition the CO 2 distribution is obtained for the cases of internal ventilation in fresh air mode and on/off control of the recirculation mode. Two different ventilation distributions were considered: one for the heating mode and one for ventilation and cooling modes. A stratification of the CO 2 along the vertical axis is shown in both the cases. While in heating mode the CO 2 concentration decreased going from the bottom to the top of the cabin, in the other two modes the CO 2 level was maximum at medium height and minimum at the extremities. The optimal positioning of the CO 2 sensors is obtained for the three operating modes.

This work deals with the assessment of the benefits, in terms of energy saving, given by the measurement of the CO 2 concentration inside the cabin of an electric crane to control the air recirculation. An experimental set-up, where a flux of 66 g/h of pure CO 2 is introduced inside the cabin, to simulate the breathing of a driver, is used to compare two different ventilation strategies, in heating and cooling conditions. With the first control strategy the air recirculation is always off. With the second one the air recirculation on/off system is controlled on the bases of the CO 2 levels in the cabin air. The power consumed by the positive temperature coefficient (PTC) heater (in heating mode) and by the compressor of the refrigeration cycle (in cooling mode) is measured in the two cases. The value of the energy consumption along the test duration is used as parameter to assess the energy saving effect of the air recirculation. The results show that the air recirculation based on the CO 2 concentration inside the cabin allowed an energy saving of the 53.8% and 72.6% in the cases studied in heating mode and of the 0.8% and 9.0% in the cases considered in cooling mode.

This paper presents an experimental study on inductive current transformers. Their modelling is still a key topic among their literature and the related studies are quite vivid. To this purpose, the paper contributes to the improvement of the transformers' behaviour knowledge under typical operating conditions. In particular, a procedure is proposed to predict ratio error and phase displacement of the current transformer by starting from a fixed loading current and ambient temperature. Moreover, a decomposition procedure is performed to analyse the filtering behaviour and the contribute of the current transformer shunt parameters. Results show the effectiveness of the presented procedure and how the shunt parameters affect the overall ratio error and phase displacement.

With the purpose of understanding more and more the causes of fault for MV cable-joints this paper deals the interfacial pressure vs. temperature issue. By starting from results obtained by the authors in the field of cable- joints, firstly a test bed for pressure measurements is developed and characterized. Afterwards temperature test cycles have been defined to measure how temperature affects the interfacial pressure (XLPE/Silicon rubber) inside the cable-joints. Presented results confirm the accuracy of the developed setup and the pressure vs. temperature behaviour of two different cable-joints.

Joints are critical components of MV cable distribution networks and the aging rate of their insulation is particularly sensitive to temperature due to loading current and laying environment parameters. This makes it very useful to monitor the load current and laying environment parameters (humidity, pressure and temperature) of joints, so as to single out conditions that might accelerate joint insulation aging rate critically. This paper illustrates the installation of humidity, pressure, current and temperature sensors - in a partnership between e-distribuzione (the main DSO in Italy) and the University of Bologna - to assess the aging rate of cable joint insulation in underground distribution networks.

As reliable power network is crucial to deliver promised electric power, cable powerline monitoring in medium voltage networks has a great importance for Distribution System Operators (DSOs) all over the world. A considerable rate of failures in cable powerlines is referred to the cable joints. Especially during the summer period, an excessive number of joints are subjected to explosion, causing outages in different points of the power network. To this purpose, in this paper, a simple and cheap test setup has been designed and calibrated to perform one of the key measurements for the cable monitoring, Tan Delta. Finally, the Tan Delta of different joints have been measured using the proposed setup.

Even if their deployment in electrical medium voltage networks was not as extensive as could be expected at the beginning, Phasor Measurement Units are key elements for Smart Grid operation. An impressive amount of papers discusses their implementation and usefulness in medium voltage network and almost as many deals with their metrological characterization. Although it is well known that instrument transformers are the main source of uncertainty in PMU-based synchronized measurements, this topic is not sufficiently tackled in the scientific literature. In this paper, the attention is focused on the calibration of a measurement system made by a PMU and a low-power instrument transformer commonly employed in the Italian distribution network.

The paper presents a novel mathematical approach for assessing the phase angle displacement of voltages at nods of a power network with respect to a node taken as reference. It is accomplished without the use of a global time-reference signal, like those provided by GPS technology or through wired connections. This study origins from the growing interest of Distribution System Operators (DSOs) to deploy Distributed Synchronized Measurement Systems (DSMS) in their power networks (like, in particular, the Phasor Measurement Units) for enhancing the stability and reliability of the networks. There are circumstances where bringing a time reference signal to remote PMUs is a difficult task. The paper provides an alternative solution to evaluate phasors in Distribution lines with no need of a global time reference.

AMPS 2015, sponsored by the IEEE Instrumentation and Measurement Society and organized by the TC39 "Measurements in Power Systems", is the 6th edition of the international workshop on Applied Measurements for Power Systems. It is primarily focused on the analysis of measurement issues in modern electric power networks as well as on encouraging discussion among experts coming from academia, from industry and electric utilities.

This paper illustrates the development and the experimental validation of a life model for LEDs subjected to thermal stress. The basis is the Arrhenius model for electrical insulation. The parameters of the life model are derived from accelerated life tests carried out on five samples of LEDs emitting light of different colours, namely red, green and blue. Each sample was subjected to a given value of constant temperature until the failure of all specimens. The diagnostic property for denoting failure is the residual light emitted by the LEDs under rated forward current, monitored continuously by a diagnostic system controlled via LabView. This study is the first step of an investigation whose ultimate goal is characterizing the endurance of LEDs having different colours to the stresses they face on duty, among which temperature is often one of the most challenging.

The big changes in indoor illumination caused by the introduction of LED-based devices may have effects on the health and well-being of the persons that are still under study. From the point of view of flicker, these changes further highlight the inadequacy of the current international standard. With the aim of providing a contribution to a matter that involves several scientific disciplines, new results on pupil responses induced by RGB flickering stimuli are presentedin this paper. Tests on volunteers have been performed to evaluate the inter- and intra-subject variability of pupil responses induced by the above stimuli.An instrument formerly developed (and described in previous paper) has been usedto investigate the pupil response. The results of this extensive measurement campaign are presented and discussed.

Window-type current transformers are widely used in medium voltage switchboards for measuring the current flowing in the cables entering the board itself. Due to their operating principle, the accuracy of such kind of current transformers may vary depending on many factors, such as, for example, the position of the cable passing through the transformer with respect to the center of the window and the proximity of the other cables. In this paper a procedure for assessing the metrological characteristics of window-type current transformers is presented and discussed along with the results of experimental tests.

Instrument transformers presently used in distribution networks suffer of well known drawbacks that does not allow their employment in the so-called “smart meters” that will be used in the upcoming smart grids. Among several scientific proposals for smart grid sensors, the only current transducer that, up to now, seems to play a role in the next measurement instrumentations is the Rogowski coil given that some major manufacturers are proposing it on the market. However, there is still interest for devices that can be easily installed in existing switch-boxes. In this connection, a current sensor based on a smart measurement of the magnetic field produced by the primary current is proposed. Its performances are evaluated by means of simulations relying on a suitably developed sensor model.

Semiconductive materials are widely used in power systems components such as cables and connectors. Their role is to shield and control electric fields emitted by primary components thus helping to fulfill, amongst other things, electromagnetic compatibility (EMC) requirements of the kind of the apparatus in which they are used. In this paper the behavior vs. frequency of such semiconductive materials is studied and it will be shown the trend of shielding behavior vs. frequency. In particular at frequencies greater than very few kilohertz, such as those produced by higher harmonics or transient disturbances, such properties strongly decrease.

Unplanned power system islanding is usually seen as a major risky operating condition and specific countermeasures are applied in order to avoid it. However the capability of voluntary disconnection from the external grid and autonomous operation is often a requirement for some industrial power systems and power plants. The panel session at the 2012 IEEE Innovative Smart Grid Technologies Conference on “Power system islands, autonomous microgrids and relevant instrumentation” aims at providing an occasion to exchange ideas and experiences in order to envisage situations in which voluntary power system islanding may be useful and to define the instrumentation required for a reliable operation in islanded conditions. This paper, provided by the organizers, reviews some activities recently carried out on this topic at their institution.

The international standard EN 61000–4–15 gives functional and design specifications for the Flickermeter currently used to evaluate the flicker severity, as defined in the International Electrotechnical Vocabulary. That instrument doesn't work properly if light sources different than incandescent-filament one are considered. This paper is aimed at presenting a step towards an innovative Flickermeter which is able to account a larger variety of luminous sources. In particular, the goal of this study is to find a new method to define the human annoyance under flicker condition, based on the measurement of the pupil size in presence of different flicker stimuli. The design and characterization of an automatic system able to generate flicker and measure the pupil size will be presented. In addition, the results obtained on human subject will be illustrated.

The present paper addresses the topic of fault location in power networks with cable lines. In the era of smart-grid the demand of intelligent measurement systems capable of providing quickly and with high accuracy the right location of faults in power networks is growing fast. Many proposals can be found in literature relevant to different approaches. Some commercial instrumentation is also available on the market for this purpose. Protection relays implementing this feature can either be found. This paper presents the experimental results of a measurement campaign carried out in the MV power network in the city of Milan (Italy). For this purpose the local Utility (A2A SpA) is using a commercial distributed measurement system (the ALTEA FLS) for locating both faults and also fast transients due to customers' loads operation. Preliminary experimental results have shown good performance. They have been better analyzed in order to investigate over the reliability and the accuracy of such measurement system. © 2011 IEEE.

This paper deals with a life model for low voltage polyester- insulated capacitors subjected to time-varying temperature. The results of accelerated life tests performed on low voltage polyester-insulated capacitors at various temperatures are illustrated and from them a constant-temperature life model is derived. Such model, inserted within a “Miner’s law” framework, gives rise to a variable-temperature life model that is compared with the results of subsequent life tests performed on the same kind of capacitors under daily temperature cycles. This is a milestone towards real-time life estimation of capacitors subjected to time-varying temperature, as well as towards the extension of this approach to other electrical devices.

Life models relate the time to failure to the applied stress. They can be derived starting from knowledge of chemical/physical phenomena involved in the ageing process caused by the stress or by means of regressive techniques on data acquired in ALT-based procedure. Anyway, experimental tests are needed. This paper deals with a test system implemented to estimate a life model for LEDs where the forward current is considered as stress.

The role of reliability prediction during the design stage of a system is worldwide recognized. Simulation tools and proper experimental approaches are usually applied to get reliability properties. In this paper, an experimental method relying on the use the dynamic stress-strength approach is presented and applied on a simple electronic device. The obtained results are presented and discussed.

The subjectivity and the limitation of the standard method for the flicker evaluation have suggested the research of different approaches. The intent is to achieve objective information on the state of annoyance of a human being subjected to light flicker. Recently, a technique based on the analysis of the pupil size variation has been proposed. This paper studies the effects of different light stimula on pupil diameter and highlight some interesting results.

Voltage transients are the main causes of complaints for medium-voltage customers, and hence interest is focused on investigation techniques able to help in classifying and localizing such events in accordance with their origin. In this light of fact, a distributed measurement system for performing synchronized acquisition of fast voltage transients is presented in this paper. The system, designed to fulfill specific constraints about the reliability of the provided information, has been used in a one-year long measurement campaign performed in a medium voltage network. The main obtained results are presented.

The problem of determining the location of a fault in an electrical power network can be faced by using a distributed measurement system. This paper deals with the metrological characterization of the remote units of the system, so that the combined uncertainty affecting the fault position can be evaluated. A numerical approach has been used in this paper for the uncertainty estimation. Results are presented and discussed.

Flicker annoyance measurement, no matter if it is performed by processing the supplying voltage or by evaluating the light emitted by the lamp, relies on the assumption of a proper model of the behavior of the complex eye-brain system in presence of fluctuating light. The only experimental data available are the ones obtained, for a certain incandescent lamp, by asking several people to report their perception about flicker they were subjected to. In this paper, the possibility of achieving an “objective” evaluation of the flicker effects on human subject is investigated. In particular, the increment of the blood flow in a vessel at the optic nerve papilla is considered and taken as possible index of the annoyance due to flicker.

The Remote Didactic Laboratory Laboratories Didattico Remoto - LA.DI.RE. "G. Savastano" is the e-learning measurement laboratory supported by the Italian Ministry of Education and University. It provides the students of electric and electronic measurement courses with the access to remote measurement laboratories delivering different didactic activities related to measurement experiments. The paper describes the innovative aspects concerning the software and hardware architecture, and the delivered services to both the teachers and students. The core of the delivered services is the integration of the learning measurement system with the remotely accessible measurement laboratories through the Web. Moreover, the advantages of the proposed software and hardware architecture are highlighted in comparison with the traditional architectures

The use of a distributed measurement system to locate the source of transient voltages is discussed in this paper. The system implements a method based on the measurement of the starting instants of a transient in the nodes of the monitored network. The method performance is investigated by simulating the system operation. Results in the case of both faults and insertion of capacitors in a IEEE test network are presented and discussed.

The paper presents the results of a study performed on a measurement system for voltage fast transients detection and characterization in medium voltage power networks. Such a system is thought for working in stand-alone mode for a preset number of months and far away. To this the system reliability study (performed by means of the Markov technique) have been carried out along with the implementation onto the system of a remote-monitoring & self-diagnostic procedures for assuring correct operating conditions by means of both preventive or corrective maintenance of the system. In the present paper the architecture of the self-diagnostic & remote-communication system along with the results of the system reliability study will be presented and discussed.

The response of the human eye to flicker depends on the type of lamp used. The standard flickermeter is based on the measurement of voltage and assumes the light source to be a 60 W incandescent lamp. When a different lamp is the source of light flicker, the standard flickermeter gives erroneous results. This paper presents a dynamic model of the eye-brain response to flicker. The model is based on the analysis of the light emitted by the lamp. A suitable measurement system has been developed and three different kinds of lamps have been considered. Experimental results show how the emitted light spectra and the human eye response to different colors determine the level of annoyance.

The Remote Didactic Laboratory Laboratorio Didattico Remoto ? LA.DI.RE. "G. Savastano" is the e-learning measurement laboratory supported by the Italian Ministry of Education and University. It involves about twenty Italian universities and provides the students of electric and electronic measurement courses with the access to remote measurement laboratories delivering different didactic activities related to measurement experiments. In order to demonstrate the versatility for didactic use, the overview of same experiments is given. The didactic experiments summarized in the paper concern with: measurement characterization of instruments and communication systems, measurement devices for remote laboratory, basic electrical measurements, magnetic measurements, electromagnetic interferences measurements, and signal processing for measurement applications.

Determining the trend over long time interval of parameters characterizing electrical power systems usually requires high storage capacity. The authors have proposed a measurement technique, based on both a random sampling strategy and a statistical approach, which allows to reconstruct the trend of a given parameter by processing a very limited amount of data. In this paper, a smart system implementing such a technique is presented. It is a microcontroller-based device devoted to the acquisition of the rms values on low voltage systems. The results of some experimental tests showing the good performance of the implemented device are also presented and discussed.

There is a search for investigation techniques capable of characterizing voltage transients, which are one of the main causes of power quality degradation, and classifying them depending on their origin. In a previous paper, the use of a distributed measurement system for power quality monitoring in parallel with a lightning location system was proposed to assess whether a lightning event is responsible for a voltage transient. An accurate estimate of the transient's starting instant is required to tackle that task. In this paper, a system for the measurement of the starting instant of impulsive voltage transients is proposed and the procedures for its metrological characterization are described. The results of the characterization tests are also reported and discussed.

In this paper, an instrument based on the virtual instrumentation (VI) technique is presented. It allows estimating the trend of electrical quantities in power systems over long observation intervals by acquiring and processing a limited amount of data. An application example dedicated to a daily current profile estimation is presented and the relevant combined standard uncertainty, arising from the uncertainty sources located in the measurement hardware, is evaluated. Finally, the results of a statistical test are presented aiming at verifying the correctness of the gauged relationship.

Voltage transients are the main causes of complaints from medium-voltage customers. For this reason, utilities and independent authorities are focusing their attention on investigation techniques capable of providing information useful for classifying voltage transients depending on their origin. Distributed measurement systems for power quality monitoring able to detect, measure, and classify impulsive transients can be used in coordination with lightning location systems to assess whether there is a relation between a given transient and a lightning event. In this paper, a criterion for evaluating the above correlation is proposed and a numerical example, which is based on real accuracy specifications, is presented. The results show that attempting a correlation between lightning events and induced transients is quite reasonable. © 2004 IEEE.

Owing to the proliferation of loads which draw nonsinusoidal currents, the current and the voltage distortion in public distribution systems is ever increasing. The usual online investigation methods cannot provide information about the responsibility for harmonic distortion in a given metering section. New methodologies are therefore searched for. Some recently proposed investigation techniques are recalled in this paper and the relevant measurement problems are discussed. A digital measurement system which is based on the virtual instrumentation (VI) technique and implements these methods, is described. The results of some experimental work are also presented.

Modern instrumentation for the monitoring of electrical power systems is based on digital signal processing (DSP) techniques. If suitable design choices are made, the overall accuracy of this kind of instrumentation basically depends on the signal conditioning circuits. They have outputs proportional to the input to drive the A/D converters and are very often based on instrument transformers to ensure the isolation between the instrumentation and the monitored power system. This paper presents a lab prototype of a digital instrument for the calibration of current-to-voltage transducers (CVT's) and discusses its performance. The results of calibration tests performed on some commercial active and passive CVT's are also reported.